使用HttpClient获取进度信息

我想使用'Windows.Web.Http '实现进度条。Windows Phone 8.1 Silverlight.

Edit: First Attempt:

private async Task CheckProgress()
{
    var df = httpClient.GetAsync(new Uri(uriString, UriKind.Absolute)).Progress = Progress;
    // here i want to stop the execution till whole content downloaded
    // Reason to wait here
    // this client download will be used by one more async method. so i need to wait here till the file completely downloaded.
    // this whole is done in this method only ( requirement)
} 
private void  Progress(IAsyncOperationWithProgress<HttpResponseMessage, HttpProgress> asyncInfo, HttpProgress progressInfo)
{
   // here i getting the progress value.
   // i have already set a call back method that report the progress on the UI.
}

再次尝试:但是得到异常Invocation of delegate at wrong time.

private async Task CheckProgress()
{
    var df = httpClient.GetAsync(new Uri(uriString, UriKind.Absolute))
    df.Progress =  Progress;
    await df;
    // here i want to stop the execution till whole content downloaded
} 

:

所有，我想要的是停止CheckProgress()方法保持等待，直到整个下载完成。

private async Task CheckProgress()
{
    var df = httpClient.GetAsync(new Uri(uriString, UriKind.Absolute))
    df.Progress = (res, progress) =>
    { 
       // no separate event handler.
    }
    await df;   
}